Leroy Sané must wonder what more he can possibly do to prove himself.

Last season, his second campaign with Manchester City, he was instrumental in the club's title success, providing more assists that anyone else in the Premier League and being named PFA Young Player of the Year.

But it wasn't enough to earn him a place in Germany's squad for the 2018 World Cup. And now, despite an increase in productivity this season, he appears to have slipped out of Pep Guardiola's circle of trust.

Sané was left out of the starting XI for City's Champions League quarter-final showdown with Tottenham Hotspur at the north London club's impressive new stadium on Tuesday night, with Raheem Sterling and Riyad Mahrez preferred in the wide positions.

With City trailing 1-0, Guardiola waited until the 89th minute to introduce Sané, along with Belgian playmaker Kevin De Bruyne. It was too little, too late; the potential game-changers were unable to foster an equaliser for the away side with such a limited opportunity.

On the face of it, there was nothing outrageous about Guardiola selecting Sterling and Mahrez for the game, his best player this season and a £60million summer signing.

But there's a directness to Sané's play that no other City attacker can equal.

Sterling has been exceptional this tern and is well worthy of selection in City's strongest XI, but even he can't match the sheer frightening force of Sané's speed and ability to deliver decisive cut-backs or lash rasping finishes into the corner without breaking stride.

And Mahrez is a wonderfully skilled winger, but he is not as intimidating a prospect for opposing defenders as Sané.

In a tight, tense Champions League last-eight tie – especially one away from home, where the ability to counter rapidly often proves key – it was bizarre that Sané's involvement was so minimal.

This could perhaps be attributed to Guardiola's tendency to overthink his tactics when preparing for an away game in the Champions League knockout rounds; his record of just six wins from 26 such fixtures is alarming considering the teams he has managed.

But the mistrust of Sané has been creeping up all season. It seems, to Guardiola, the 23-year-old German forward is no longer the man for the big occasion. As journalist Jack Pitt-Brooke pointed out after the Spurs defeat on Tuesday, Sané's last five starts have come against Cardiff City, Swansea City, Schalke, West Ham United and Newport County.

His last appearance in City's starting XI for a game against what would be considered top-class opposition was the 2-1 victory over Liverpool on January 3.

Sané, one of the side's star performers in last season's 100-point title romp, has started just 19 of City's 32 Premier League games this term, meaning, even if he starts every remaining fixture, he will not match his tally of 27 starts from last term.

What's most remarkable about Sané's reduced influence of late is that he has been more productive this season than he was during his breakout 2017/18 campaign.

Last term, with ten Premier League goals and 15 assists, Sané was directly involved in a goal every 96.9 minutes. This season, that average has improved to a goal involvement every 89.9 minutes.

It's a similar story in the Champions League, too. Sané has score four goals and registered four assists in Europe's premier club competition this term, from just four starts and three substitute cameos. He failed to score at all in the Champions League last year, and only notched two assists from nine total appearances (seven starts).

As they continue to chase an unprecedented quadruple, City still face significant tests before season's end – they must play Spurs twice more before a Manchester derby at Old Trafford.

For the sake of their bid for yet more historic success, Guardiola must rediscover his trust in Sané.

Manchester City